One of the nuclei occurring in four groups found in the hypothalamus. Hypothalamic nuclei include the dorsomedial, intercalatus, lateral, mamillary (lateral and medial), paraventricular, posterior, supraoptic, tuberal, and ventromedial. The cells of these nuclei secrete oxytocin and antidiuretic hormone. These hormones pass through the efferent fibers of the infundibular stalk to the posterior lobe of the pituitary gland, where they are stored until they are released.